The present invention is directed, in general, to heat dissipation for power electronics switching voltages above normal electrical isolation ratings and, more specifically, to providing a common heat sink for multiple power electronics integrated circuit devices connected in series and switching voltages for driving artificial lift equipment within a borehole.
Many power electronics semiconductor integrated circuit devices are currently employed in connection with power and control systems for production within a borehole. In particular, integrated circuit devices may be employed to step-up (i.e., increase) the voltage of power produced for transmission into the borehole from a power source such as a generator or a connection to a local fixed power grid. Power electronics integrated circuit devices are typically connected between the power source and the filter(s) and drive employed to generate the specific voltage waveforms transmitted into the borehole to power artificial lift equipment within the borehole.
Heat dissipation requirements of power electronics integrated circuit devices generally require that the integrated circuit packages be mounted on a heat sink (or, equivalently, a xe2x80x9cheat spreaderxe2x80x9d), electrically isolated from the normally-metallic heat sink material by an interposed dielectric material. The rated electric isolation for an integrated circuit device capable of switching voltages up to 1200 volts is usually about 2500 volts.
When multiple integrated circuit devices are mounted to one or more heat sinks at a common voltage potential, generally no problems arise as long as the system operates only at voltages within the electric isolation ratings. However, when the integrated circuit devices are connected in series to increase the system voltage for use with xe2x80x9cmediumxe2x80x9d voltage drives operating at 4-6 kilovolts (kV), the conventional base isolation becomes inadequate.
Moreover, in designing electrical power systems for use with production from a borehole, various considerations not germane to other applications of electrical power systems must be taken into account. Climatic conditions, in particular, must be considered since the equipment must be located proximate to the borehole, typically at an outdoor location subject to inclement weather conditions and, in the case of subsea wells, on a production platform. While the power electronics and drive may easily be contained in a weatherproof enclosure, the heat sinks employed for the power electronics preferably include at least one externally exposed surface for cooling purposes.
There is, therefore, a need in the art for improved design of heat sinks to be employed in connection with power electronics for medium voltage drives.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide, for use in an electric power system for borehole production, a heat sink structure increasing the dielectric, strength of isolation for power integrated circuits. The heat sink structure is formed from a common layer on which laterally spaced isolated layers for each individual integrated circuit are mounted. At least the isolated layers are formed of anodized aluminum coated with aluminum, oxide on exterior surfaces. The aluminum and aluminum oxide of the isolated layers provide good thermal conduction for heat dissipation while the electric isolation from the common electric potential of the common layer is improved, at least in part, by increasing the distance between the integrated circuits and the common layer. The heat sink structure may be mounted within a weatherproof enclosure with one externally exposed surface for heat dissipation.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9corxe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives, thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, whether such a device is implemented in hardware, firmware, software or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases.